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Scientists have made their most accurate measurement yet of the mass of a mysterious neutrino particle. ... A neutrino is capable of passing through a light-year (about six trillion miles) of lead without hitting a single atom.

The results of a high-profile Fermilab physics experiment involving a University of Michigan professor appear to confirm strange 20-year-old findings that poke holes in the standard model, suggesting the existence of a new elementary particle: a fourth flavor of neutrino.

Neutrinos are among the fundamental building blocks of matter. They swarm all about us. The Sun, for example, releases them in huge quantities when it fuses hydrogen to make helium - the raw nuclear process at its core. They are, however, very difficult to study because they interact so weakly with normal matter. Hence, their nickname - "ghost particles". Nonetheless, scientists have been able to discern three flavours - electron...

The collaboration behind the finding in September that neutrinos may travel faster than light has carried out an improved version of their experiment - and found the same result. If confirmed by other experiments, the find could undermine one of the basic principles of modern physics.

The mystery surrounding the source of the highest-energy particles known in the Universe has grown deeper. The particles, known as cosmic rays, can show up with energies a million times higher than the biggest particle accelerators on Earth can produce. Astrophysicists believed that only two sources could make them: supermassive black holes in active galaxies, or so-called gamma ray bursts. A study in Nature has now all but ruled out gamma...